Tapio Ihanamäki

Expression of type II and IX collagen isoforms during normal and pathological cartilage and eye development

Abstract Cartilage collagens type II and type IX exist in two alternative forms which arise from alternative splicing and alternative use of promoters, respectively. In the present study we analyzed temporal and spatial expression patterns of the two isoforms of type II and type IX collagen transcripts as well as those of α2(IX) and α3(IX) collagen mRNAs in limb cartilages and eyes during mouse embryonic development. Northern and RNase protection assays revealed temporal coregulation of the two alternative isoforms in limbs, but not in the eye where no long form of α1(IX) collagen mRNA was detected. Although in situ hybridization of limbs revealed identical expression patterns of the long form of type II collagen and the short form of α1(IX) collagen mRNA in the perichondrium and periosteum of 14.5–18.5-day embryos, the patterns were distinctly different at day 12.5 of development: the long form of type II collagen mRNA was expressed throughout the developing cartilaginous anlage whereas the short form of α1(IX) collagen mRNA was expressed in the surrounding mesenchyme. Some differences were also detected in the temporal and spatial expression patterns between the α1(IX), α2(IX), and α3(IX) collagen mRNAs. In the eyes, α2(IX) collagen mRNA had highest expression levels at day 12.5, whereas α1(IX) and α3(IX) collagen mRNAs peaked later, at day 16.5. In the limbs, α1(IX) and α3(IX), but not α2(IX), collagen mRNAs were detected in periosteal cells after 16.5 days of development. In transgenic Del1 mice, harboring type II collagen transgenes with a small deletion mutation, expression of mutant mRNA affected neither the alternative splicing of wild-type or mutant transcripts nor the ratio of the two alternative forms of the α1(IX) collagen mRNA. Despite some distinct similarities, the two alternative forms of type II and type IX collagen must, therefore, be under differential control during mouse development.

The effect of deep sclerectomy on intraocular pressure of normal‐tension glaucoma patients: 1‐year results

Purpose:  To study the intraocular pressure (IOP)‐reducing effect of deep sclerectomy on normal‐tension glaucoma (NTG) patients.

Dexmedetomidine versus propofol for sedation in patients undergoing vitreoretinal surgery under sub-Tenon's anesthesia

Purpose: The purpose of this study was to evaluate the hemodynamic, respiratory effects, the recovery profile, surgeons, and patients satisfaction with dexmedetomidine sedation compared with those of propofol sedation in patients undergoing vitreoretinal surgery under sub-Tenon’s anesthesia. Methods: Sixty patients were enrolled in this prospective, single-blind, randomized study. The patients were divided into two groups to receive either dexmedetomidine (group D) or propofol (group P). Sedation level was titrated to a Ramsay sedation scale (RSS) of 3. Hemodynamic and respiratory effects, postoperative recovery time, analgesic effects, surgeons and patients satisfaction were assessed. Results: Both groups provided a similar significant reduction in heart rate and mean arterial pressure compared with baseline values. The respiratory rate values of the dexmedetomidine group were significantly higher than those in the propofol group. The oxygen saturation values of the dexmedetomidine group were significantly higher than those of the propofol group. The expired CO2 was similar in both groups. Postoperatively, the time to achieve an Aldrete score of 10 was similar in both groups. Dexmedetomidine patients have significantly lower visual analog scale for pain than propofol patients. The surgeon satisfaction with patients’ sedation was similar for both groups. The patients’ satisfaction was higher in the dexmedetomidine group. Conclusion: Dexmedetomidine at similar sedation levels with propofol was associated with equivalent hemodynamic effects, maintaining an adequate respiratory function, similar time of discharge from PACU, better analgesic properties, similar surgeon’s satisfaction, and higher patient’s satisfaction. Thus, dexmedetomidine may prove to be a valuable adjuvant for sedation in patients undergoing vitreoretinal surgery under sub-Tenon’s anesthesia.

Expression of Sox9 and type IIA procollagen during ocular development and aging in transgenic Del1 mice with a mutation in the type II collagen gene.

Purpose To study the expression and distribution of transcription factor Sox9 and type IIA procollagen in the developing and aging eyes of normal and transgenic Del1 mice carrying proa1(II) collagen transgenes with a short deletion mutation, which cause ocular abnormalities in this mouse line. Methods The eyes of Del1 mice were studied on embryonic days E14.5, E16.5 and E18.5, and at the ages of 4 and nine months, using their nontransgenic littermates as controls. Sox9 and proa1(IIA) collagen were detected by RNase protection assay and immunohistochemistry. Results RNase protection assay revealed Sox9 transcripts in the eyes of Del1 and control mice during development and aging. The mRNA for type IIA procollagen had a similar temporal expression pattern. On embryonic days E14.5, E16.5 and E18.5, Sox9 was located by immunohistochemistry in the nuclei and type IIA procollagen in the extracellular space of the developing retina. During growth and aging, the ocular expression of Sox9 mRNA and the immunohistochemical reaction for Sox9 antibody diminished, concomitant with the reduction in type II procollagen mRNA. However, at the age of nine months, levels of Sox9 and type IIA procollagen mRNAs were higher in the degenerating eyes of Del1 and control mice. Conclusions The similarities in the temporo-spatial distribution of Sox9 and type IIA procollagen suggest that this transcription factor is involved in the activation of type II collagen expression in the eye, as has been demonstrated in prechondrogenic mesenchyme and immature cartilage. The increased production of Sox9 and type IIA procollagen in the aging retina and vitreous is analogous to degenerating articular cartilage where attempted tissue repair has also been observed.

Ultrastructural characterization of developmental and degenerative vitreo-retinal changes in the eyes of transgenic mice with a deletion mutation in type II collagen gene.

Purpose. Molecular genetic analyses have clearly associated vitreoretinal degeneration with mutations in the type II collagen gene, but lack of experimental models has prevented systematic analyses of the occurrence of phenotypic changes and of the pathogenetic mechanisms involved. The present study is a detailed morphological and ultrastructural analysis of the vitreoretinal consequences of a small deletion mutation in the type II collagen gene. Methods. The eyes of Del1 mice carrying six copies of proa1(II) collagen transgene with a small deletion mutation were analyzed during embryonic development, postnatal growth and aging using their nontransgenic littermates as controls. Tissue samples were processed for light and electron microscopy for morphological and ultrastructural analyses. Transcription of proa1(II) collagen gene was localized by in situ hybridization, and type II collagen was detected by immunohistochemistry. Results. In this mouse model most components of the eye are ultrastructurally unaltered. However, the transgenes caused a dose-dependent dominant negative effect seen as a reduced number of type II collagen fibrils in the vitreous. In concert with this, dose-dependent accumulation of amorphous material was observed in the dilated rough endoplasmic reticulum of cells responsible for the production of type II collagen molecules. In mice homozygous for the transgene locus, the vitreoretinal degenerative lesions appeared already during late embryonic development. In mice heterozygous for the locus, such changes were milder and appeared only during postnatal growth and progressed gradually upon aging. Conclusions. The observed ultrastructural changes suggest that defective structure and function of collagen fibrils in Del1 mice result from a partial block in the post-translational processing and secretion of the mutated procollagen chains, and partly from secretion of mutated procollagen molecules which interfere with normal fibrillogenesis.

Ocular abnormalities in transgenic mice harboring mutations in the type II collagen gene

Purpose. To characterize the morphological changes in the eyes of transgenic mice harboring different mutations in type II collagen gene to elucidate the function of this collagen in the eye, and to find out whether these animals could function as models for the human arthro-ophthalmopathies of the Kniest, Stickler and Wagner types. Methods. Three genetically engineered mouse lines representing two types of mutations in the triple-helical domain of type II collagen and their nontransgenic littermates used as controls were analyzed on day 18.5 of embryonic development. After genotyping by polymerase chain reaction (PCR) and Southern hybridization the embryos were prepared for routine histology. Polarization microscopy was done on hyaluronidase-treated sections. Results. Histological analysis revealed several genotype-dependent abnormalities in the eyes of the transgenic mice. Most striking changes were observed in the vitreous architecture; in one line of mice the vitreous was tightly packed in the posterior region of the vitreous space with thick fibrils, empty cavities and dense membrane-like material. The other mutation resulted in reduced filament density of the vitreous. In the most severely affected phenotype the internal limiting membrane was detached from the retinal layers and was markedly thickened, and the posterior lens capsule was thickened. The anterior chamber was shallow or absent in all transgenic lines but was well formed in the normal animals. Changes were also observed in the lens, corneal and scleral structures. Conclusions. The ocular changes observed in transgenic mice harboring mutations in type II collagen gene show similarities to the human ocular findings in Kniest dysplasia, and in Stickler and Wagner syndromes. We therefore propose that these animals could serve as models for systematic analysis of vitreoretinal degeneration and other abnormalities, as seen in these syndromes.

Echovirus Type 4 as a Probable Cause of Meningitis Associated with Bilateral Optic Neuritis: A Case Report

A 30-year-old man developed bilateral optic neuritis 1 week after acute viral meningitis caused by echovirus type 4. He received a high-dose steroid treatment combined with intravenous gamma -globulin. His visual recovery was good, and there was no sign of a primary demyelinating disease.